Variable tap transformer system



May 8, 1951 J. A. GULow VARIABLE TAP TRANsFoRMER SYSTEM 2 Sheets-Sheet lFiled April-19, 1945 sq* l d Q NW l l l l i i l I I l l I IRI l l l I Il l I l I l l l l I l l l l l l I l l l l I .lll-

- IN VEN TOR. c/o-/f/v f4 aza/M May 8, 1951 J. A. GULow 2,551,943

VARIABLE TAP TRANSFORMER SYSTEM Filed April 19, 1945 l 2 Sheets-Sheet 2IN VEN TOR. f/o//N 601mm ,4 7 7 OHNE Y.

Patented May 8, 1951 UNITED STATES PATENT OFFCE 4 Claims.

This invention relates to an apparatus for providing at will a variableVoltage, such as may be required for laboratory, test and otherpurposes, and, more particularly, this invention relates to an apparatuscapable of providing a wide range of change of alternating potential.

One of the objects of this invention is to provide a compact, eiiicient,and practical apparatus for selectively providing, in suitableincrements, l

a wide range of change of voltage. Another object is to provide anapparatus of the just-mentioned character particularly adapted tofurnish alternating potential, of suitable frequency, and selectivelyvariable in suitable increments or steps. Another object is to provide asuitably variable potential from a source of substantially iixedpotential by way of switching means coacting with the source or sourcesof relatively fixed potential so that commutation is facilitated,relatively movable circuit controlling parts or cantacts are protectedagainst detrimental sparking or loading, greater compactness, and lessbulk in the conductive parts of the switching means is possible, andother advantages are achieved.

More particularly, another object is to provide a coacting transformerand switching system whereby greater compactness and lesser bulk may beachieved, both as to the transformer means and the switching meansemployed, to provide the desired range of varibility of alternatingpotential. Another object is to so interrelate, in such a system, thetransformer means and the switching means as to permit the employment ofa simpler, smaller, and more compact transformer structure, thus alsodiminishing iron losses and improving eiliciency, while at the same timeachieving improved commutation by the switching means and in a manner topermit the employment, in the switching means, of metallic conductiveswitching parts that are of small mass within the range of normal loadcurrent at the selected voltage.

Another object is to provide a practical and compact multiple switchingmeans for successively adding small increments of potential from theselected source and then successively adding such small increments tosuccessively added large increments from the selected source, with r themultiple switching means mechanically coupled for suitable commutationof one from the other and so coacting with each other and with thesource or sources of potential that destructive commutation or sparkingat the switching means does not take place and unintentional or abnormalloading of conductive parts of the switching means is avoided. Anotherobject is to carry out this last-mentioned object by achievinginherently variable rate of drive of one switching means from anotherand in relation to the available increments of the source or sources ofpotential so as, in turn, to permit |the employment of shorter lengthsof conductive parts in the switching means themselves.

Other objects are, in general, to provide an improved apparatus capableof converting a relatively fixed potential into a selectively variablepotential, and to provide such an apparatus that will be practical andsimple to manufacture, easy to manipulate, and eilicient and longlastingin action. Other objects will be in part obvious or in part pointed outhereinafter.

The invention, accordingly, consists in the features of construction,combination of elements, and arrangements of parts all as will beexempliiied in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawings, in which are shown, by way ofillustration, several possible embodiments of this invention:

Fig. 1 is a schematic and diagrammatic representation of a transformerand switching arrangement for achieving a selectively variable potentialfrom a source of relatively Xed potential, and

Fig. 2 is a diagrammatic and schematic representation of a modified formof system and apparatus to illustrate how my invention may be employedwhere electrical isolation of the system and apparatus from the initialsource of potential is desired, and to illustrate also how the multipleswitching means may be arranged for greater compactness than in thearrangement of Fig. 1.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

Referring, iirst, to Fig. 1, the apparatus may be embodied or mounted toform a single compact unit, indicated generally by the referencecharacter lll, which may represent a suitable base, or mounting, orcasing on or within which the various parts are mounted in any suitableway, and in that embodiment let it be assumed that a variable potentialis to be obtained from any suitable extraneous source of relativelyfixed potential, such as an existing power circuit or a generator. I,therefore, prefer to provide a pair of terminals i and i2 to whichconnection may be made in any suitable way, as by conductors i3 and i4,to such a source of relatively fixed potential, which isdiagrammatically indicated at i5, and i provide also two terminals bywhich connection may be made to lead or supply the variable potential towhatever load or device it is to energize, and, conveniently, 1 use oneof the terminals il, i2 and a terminal l5 for this latter purpose.Accordingly, conductors I? and i3 may be connected to the terminals iland l5 to supply the load I9 with the selectively variable, alternatingpotential.

Included in the apparatus is a transformer, generally indicated by thereference character T, having preferably a shell type of core R andwindings W1 and W2, of which winding W1 is constructed to function atthe voltage applied to the terminals Ii, l2 by the sourceiii-illustratively 110 volts-and, by conductors 2l and 22, its terminals23 and 25 are connected to apparatus terminals il, i2. Winding W1 issubdivided into a suitable number of equal sections, illustrativelythree, by suitable taps that are connected to terminals 24 and 25. Whenenergized, winding W1 can function as the primary winding, with respectto which W2 is the secondary winding, and the latter is preferablyconstructed to have induced in it a voltage equal to the voltage of anyone of the equal sections S1, S2, and S3 of the winding W1. Thus thetotal number of turns of winding W2 is equal to the number of turns ineach of the equal sections of winding W1.

Secondary winding W2 is, in turn, subdivided into the desired number ofpreferably equal sections or increments-illustratively four sections A,B, C, and D-by suitable taps or terminals 33, 3|, 32, 33, and 34.

The taps or terminals 23 to 25 of winding W1 are connected to contactsegments of a rotary switch structure, generally indicated by thereierence character 35, and the terminals or taps 33 to 34 are connectedto contact segments of another rotary switch structure, generallyindicated by the reference character 35, the two switches being suitablycoupled together for timed actuation of one by the other, preferably inthe manner later described. These switches are so arranged and are madeto coact with one anotherin such a way that there may be made available,at the output terminals lli-i I, a voltage that is variable throughout arange from a fraction of the voltage of a section of winding W2 up tothe voltage of the winding W2, plus the voltage of as many sections ofthe winding W1 as may be desired.

Switch 36 preferably comprises a suitable number of contact members,being in number equal to the number of taps from winding W2, plus two,and they are preferably metallicillustratively in the form of at arcuateplates arranged in a circle, being suitably mounted upon a suitableinsulating plate or base, indicated at 31; they may be proportioned andspaced from each other substantially as indicated in the drawing, for afour-sectioned winding W2, and they comprise contacts E and F which arepositioned in diametric opposition and are of relatively substantialarcuate extent, leaving substantially equal upper and lower arcuatespaces between their respective ends; in the upper arcuate spaces arepositioned three Contact plates G, H, and I, and in the lower arcuatespaces are positioned two Contact plates J and K. Relative 4 arcuatelengths and spacings are substantially as shown in the drawing.

Through the mounting plate 37 extends a shaft 38, rotatably supported inany suitable bearings (not shown) the shaft being provided yat itsforward end with suitable means, such as a hand wheel 39, by which itsrotational movements may be controlled. Shaft 3S, in turn, actuates twodiametrically opposed brushes 4i and 42 which are adapted to engage theyabove-mentioned contact plates E to K, and they may be mounted in anysuitable manner to be driven by the shaft 38. Thus there may beprovide-d a hub 43 of insulating material, suitably secured to the shaft38 andcarrying the brushes 4i and 42. The brushes 4l and 32 areconnected to the respective ends of a suitable voltage divider, whichcon- Veniently takes the form of a resistance 44 and which is providedwith a tap 45, usually positioned at the midpoint of the resistance 44but preferably shiftable or adjustable along its length for purposesl-ater described, the tap d5 being in turn connected, by conductor 46,to the output terminal I5. In order to maintain this connection of thebrusheslli and 42 to the resistance 44 for the various rotary positionsthat the brushes may assume, the brushes 1H and 42 are connectedelectrically to, or formed integrally with, arcuate .contacts 41 and 48,respectively, each being of an effective arcuate extent of substantiallydegrees and being conveniently secured to the hub 43, thus also formingthe mounting onto the hub 43 of the brushes 4l and 42 themselves. ASindicated in the drawing, the contact segments 4l and 48 areelectrically insulated from each other and, with their faces lying inthe same plane, and electrical contact with them during their rotarymovements may be effected by brushes 55 and 5I, to which the resistance44 is connected by conductors 52 and 53. Brushes 5B and 5I areconveniently carried insulatingly by the main mounting plate 37, towhich they are secured in any suitable manner, on their respective outerends, it being noted that they are constructed to be of suicient lengthto bridge over the fixed contact plates E and F from which they arespaced, being suitably bent for that purpose, so as to permit thebrushes 4| and 42 to ride in under them without contacting them.

The end terminal 30 of winding W2 is connected to contact plate G byconductor 56; tap 3l is connected to contact J by a conductor 51, tap 32is connected to contact H by conductor 58, tap 33 is connected byconductor 59 toA contact K, and the end tap 34 is connected by conductor50 to contact I.

The above-described arrangement of plate contacts for switch 36 issuitable where winding W2 comprises four sections, and is illustrative;where more sections, and hence more taps, are provided for winding W2,the number of plate contacts is increased according to thejust-described illustrative arrangement.

As for switch 35, that is, in general, constructed and arrangedsuccessively to add sections S1, S2, etc., of the winding W1 to thewinding W2, or such fractions of it or its Voltage as are made eectiveby the switch 35; switch 36 might thus be termed a ne or Vernier switch,and switch 35 might be termed the coarse switch. Switch 35 comprises asuitable support, such as a plate 52 of insulating material, havingmounted thereon arcuate contact plates, four in number where the windingW1 has three sections and, hence, has four taps; these contact platescomprise plates L, M, and O respectively connected by conductors 153-21,64, and 65 to the taps 23, 24, and 25, and a contact plate P which isconnected by conductor 66 to conductor 22, and hence to tap 26 ofwinding W1. These plates, in relative arcuate extent or length may besubstantially as indicated in the drawing.

Two contact brushes 61 and 58 are supported in any suitable way, as by ahub 19 of insulating material, on a shaft 1I which extends through thesupporting plate 62 and which is provided with suitable bearings (notshown) for rotatably supporting it in parallelism with the shaft 38 o1"the Vernier switch 36 and laterally displaced therefrom, as to theright, as shown in Fig. 1. The brushes 61, 68 are angularly displacedsubstantially as indicated, are insulated from each other in anysuitable manner-as by the structure of the insulating hub 'I0-and theyare in electrical connection, respectively, with slip rings 12 and 13coaxially carried by the hub 16, and by the latter insulated from eachother. Brushes 14 and 15, supported in any suitable way on or by theinsulating support 62, bear against the slip rings 12 and 13,respectively, so that electrical connection with the brushes 61 and 68may be maintained, regardless of what position the latter assume andalso during rotary movement thereof.

Brush 14 i5 connected by conductor 16 to tap or winding W2, and brush 15is connected by conductor 11 to contact plates E and F of switch 36.

Suitable means are provided to coordinate the rotary motion of the shaftof one of the switches to the shaft of the other switch, and this ispreferably achieved so as to provide the desired ratio of drive betweenthe two shafts and preferably, also, to achieve periodic variations inthat ratio of drive. In Fig. l an illustrative driving connectionbetween the two shafts 38 and 1I is shown, and it may comprise twoelliptical gears S0 and 8|, with a gear ratio of l to l, one of thegears being mounted on the shaft 38 and the other upon an intermediateidler shaft 62; gear SI drives a spur gear 83, conveniently coaxiallymounted with it on idler shaft 82, and, meshing with the spur gear 83,is a gear 84 secured to the Shaft 1I of the other switch. On the forwardend of shaft 38 is mounted, as above described, the

hand wheel for manually controlling the interconnected switches, and onshaft 1I may be mounted a pointer or indicator 86 to be rotated by theshaft 1l relative to a suitably graduated dial 81 so as to indicatevisually and directly the voltage which the apparatus makes availableacross the output terminals II--I6 within the range of the apparatus.

In the starting or initial position of the parts, corresponding to whichthe indicator 86 `and dial el would show minimum possible or zerovoltage, brush 4! rests on contact G and brush 42 is between contacts E'and J; brushes 61 and 68 are both in engagement with plate contact L. Novoltage is, therefore, applied across the output terminals i I-!5.

The rst increment of clockwise rotation of shaft 3S, however, bringsbrush 42 into engagement with contact J, while brush 4I maintainscontact with contact G, due to the relative positions and arcuatelengths of these parts; and brushes 61 and 58 remain in contact withcontact L. With brushes 4I and 42 on contacts G and J, respectively,section A of secondary winding W2 is impressed across the resistance 44,and any fraction of its voltage, depending upon the position of tap 45,may thus be impressed across the output terminals I6 and Il. Thecorresponding circuit arrangement is from tap 3i), conductor 56, contactG, brush 4I, contact 41, brush 50, conductor 52, resistance 44,conductor 53, brush 5|, contact 48, brush 42, contact J, conductor 51,to the other tap or terminal 3| of section A of winding W2. A conductor16, as above described, leads from the first tap 30 of Winding W2 tobrush 14, which, through slip ring 12, brush 61, contact L, conductor63, and conductor 2I, impresses the potential of tap 3S on outputterminal Il; by means of the voltage divider 44-45, any desired fractionof the voltage of section A of winding W2 may be impressed upon theother output terminal I6, so that there is applied to the load I9 avoltage variable from Zero to the voltage of section A, according to theposition of the tap 45 relative to the resistance 44. For each stage orsucceeding stage, a corresponding splitting or variation of addedvoltage may be achieved, but, for convenience in the ensuingdescription, it will be assumed that the tap 45 is in midpositionrelative to the resistance 44, though it will be understood that theabove-described variation may be, nevertheless, `achieved at each suchsucceeding step.

If, for example, the voltage of section A is one volt, the lastabove-described setting of the parts impresses a voltage of 6.5 voltsacross the terminalslandil.

The next increment of rotary movement leaves brushes 61, 68 still oncontact L, for they still partake of very small angular movement; whilebrush 4I assumes a position between contacts G andH, and brush 42engages contact J. Tap 36 remains connected to terminal I i through theengagement of brush 61 with contact L of coarse switch 35, while outputterminal I6 is now connected to tap 3i through a circuit that runs fromterminal I6, conductor 46, tap 45, th-e right-hand portion of resistance44, conductor 53, brush 5I, contact '48, brush 42, contact J, conductor51, to tap 3l, and thus the full voltage of section A is applied to theoutput terminals, through the right-hand portion of resistance 44.

The next increment of rotary motion brings brush 4I to engage contactl-I, brush 42 remaining in engagement with contact J, brushes 61 and 68of the coarse switch being still in engagement with contact L. Thisrearrangement, achieved by switch 36, places section B of winding W2across the resistance 44, thus adding half its voltage (tap 45 assumedto be at the mid-point) to terminal I6, terminal El being maintained bycoarse switch 35 connected to tap 36.

The connection of section B just described extends from tap 3i,conductor 51, contact J, brush 42, contact 4S, brush 5l, conductor 53,resistance 44, conductor 52, brush 5H, contact 41, brush 4I, contact H,conductor 58, to tap 32.

The next increment of rotary motion maintains brush 4i in engagementwith contact H and moves brush 42 into the Space between contacts J andK of the Vernier switch 36, and brush 61 of the coarse switch 35 stillmaintains contact with Contact L, but brush 68 is moved into the spacebetween contacts L and M. Thereby tap 3.6 remains connected tcoutputterminal II, and output terminal Iii becomes connected to tap 32 througha portion of the resistance 44, and thereby the voltage across theterminals il and i5 is again increased by an appropriate increment. Theresultant connec- Y tion of `terminal I6 may be traced from the latter,thence conductor 46, tap 45, left-hand portion of resistance 44,conductor 52, brush 50, contact 41, brush 4|, contact H, conductor 55,to tap 32.

The next increment of movement nds brushes 4| and 42 in Contact withcontacts I-I and K, respectively, thus bridging resistance 44 acrosssection C (taps 32-33), the mid-position of tap 45 increasing thevoltage potential added across terminals I6 and il by haii the voltageoi' section C, terminal remaining connected to tap 34, since brush t? isstill in engagement with contact L and brush 58 is about to engagecontact plate M.

The next increment of rotary movement brings brush 4| between contacts Hand I, brush 42 maintaining contact with contact K, whereby tap 33 ofsection C is connected to terminal i5 through a portion of resistance44, the circuit extending through conductor 45, tap 45, resistance 44,conductor 53, brush 5I, contact 43, brush 42, contact K, conductor 59,to tap 33, terminal continuing to be connected to tap 3i), since brush6i is still on contact L, though brush 58 has now made engagement withcontact M.

The next increment of rotary motion of switch 36 brings brush 4| oncontact I, brush 42 stili maintaining engagement with contact K, brushes61 and 68 of switch 35 engaging contacts L and M, respectively. SectionD of taps 33 and 34 is thus connected by conductors 59 and 5G across theresistance 44, and an added increment of voltage becomes applied tooutput terminal i6, ac-

cording to the position of tap 45 along the resistance R.

The next increment of motion brings brush 42 into the space betweencontacts K and E, brush 4| engaging contact I and the brushes 6i and 68of the coarse switch 35 contacting contacts L and M, respectively. As aresult a full voltage increase, represented by the voltage of section D,is now applied to output terminal le through the left-hand portion ofresistance 44, the circuit extending from tap 34, conductor 6|), contactI, brush 4|, contact 41, brush 50, conductor 52, resistance 44, tap 45,conductor 4S, to output terminal 5, and thus the full voltage of all ofthe sections of secondary winding W2 is applied to the output terminalsi i and it, and, hence, to r the load l-all in successive step-by-stepincrements which, if the tap remains at the midpoint of resistance 44,are each in an amount equal to half of the voltage of a section o1 thewinding W2; however, for any of these increments, variation or changemay be achieved by varying the setting of the tap 45. Moreover, for eachshi'l t or change resulting from an increment of rotary movement of theswitch 35, there is dependable'control of current now as the switchachieves a shift or change in circuit connections, for there isdependable control of the current undergoing commutation, due to thecoactions and presence of the resistance 44, which, as will be seen fromthe above, is in its entirety or in part always associated with acircuit being interrupted or made. Thus, for example, the resistance 44is either shun'ted across a selected section of the winding W2 ordisconnected therefrom, and thus represents a denite load. Moreover,that shunt relationship is shifted in either direction-that is,according to connection or disconnectionin relation to a preceding orsucceeding circuit arrangement in which a portion (half, if tap 45 is atthe mid-point) of the re- 8 sistance 44 is always included in the loadcir-x cuit and can thus function as a current-limiting resistance toeiect limitation upon current values affected by the commutating actionof the two switch structures.

Such coactions make it possible to avoid many of the disadvantages ofknown types of transformer-tap-changing switch constructions and,moreover, contribute toward permitting the use of smaller, and hencemore compact, conductive parts of both the Vernier switch and the coarseswitch; for example, I am enabled to use solid silver Contact elementsin small and compact form, with unusually high capacity, the commutationcontrol above described contributing also toward longer life of themoving switch parts.

Recurring to the operation of the switch mechanism, the engagement ofbrush 68 of coarse switch 35 with contact M is effective to connect theopposed long contacts E and F of Vernier switch 36 to tap 24 of theprimary winding W1, the circuit extending from tap 24, conductor 64,contact M, brush 58, slip ring 13, brush 15, and, by conductor 1I, tocontacts E and F. Contacts E and F are thus at the same potential;contact I, being connected by conductor 50 to tap 34, is at the samepotential as contacts E and F, winding W2 and section S1 being of thesame voltage or number of turns. Hence the spacing between contacts Iand F can be relatively smallsmall enough so that the brush 4i canbridge the gap between the two and engage both of them in movement fromthe one to the other. A similar relationship of close spacing existsbetween contacts G and E, which, at the outset, are at the samepotential-contact G being connected to tap 3Q through conductor 56 andcontact E being connected by conductor 11, brush 15, slip ring 13, brush68, contact L, conductor 53, and conductor 2i, to tap 23 of the primarywinding W1, taps 3i) and 23 being at the same potential; this latterrelationship exists at the start of the cycle of operations, as will nowbe understood.

The next increment of movement brings brushes 4| and 42 into engagementwith contacts E and F, respectively, thus bridging the resistance 44across these contacts through conductors 52 and 53, and during thetravel of the brushes 4| and 42 along the contacts E and F,respectively, the rate oi drive of shaft 'He-and, hence, of brushes 51and {iS-is increased, the longer radius portions of gear 8l! being nowoperative upon portions oi shorter radius on the gear 8|, so that brushSi is quickly moved 01T contact L in the coarse Switch and `brought ontocontact M with which brush 68 is still in engagement. This increasedrate ci drive of the brush parts in the coarse switch permits of greaterspacing between the contacts or" coarse switch 35 and permits, also, theuse of brushes of greater current-carrying capacity; thereby, also,contacts on the Vernier switch 35 can be of shorter arcuate length andthe structure can be made more compact, and, more particularly, contactsE and F can be made shorter and the other contacts of Vernier switch 36made longer.

With the parts in the positions just described, all of the brushes areat the potential of tap 24 of winding W1, but, as the rotationalmovements continue, brush 55 bridges contacts G and E, and brush 5|enters the space between contacts F and J, brushes 51 and 58 of thecoarse switch being still on Contact M. The voltage across outputterminals i5 and is still the same as before, being equal to the fullvoltage of Winding W2, but

that voltage is supplied by the entire section S1 of primary winding W1.Thus terminal 23 of section S1 is connected, through conductor 2I tooutput terminal I I, while tap 24 (the other terminal of section S1) isconnected to output terminal I6 as follows: from tap 24, conductor 54,contact M,

rush E8, slip ring E3, brush '55, conductor ll, brush 5d, conductor 52,left half of resistance 44, tap 45, and, by conductor 4S, to theterminal I5. Through brush B'I, slip ring '12, brush 14, and conductorl, tap 30 of winding W2 is connected to tap 24; the connection of tap 30to tap 24 is also maintained through the conductor 56 eX- tending to thecontact G, with which brush 4I is still in contact. The sameabove-mentioned voltage is thus applied to output terminals I6 and I I,but now through the left half of resistance 44.

Brush 5G now moves further so that it contacts only Contact G, whilebrush 42 is brought into engagement with contact J; this increment ofrotary movement of Vernier switch 36 shifts the coarse switch so thatbrushes 51 and E8 move further along on contact M. The voltage appliedto the output terminals is now the voltage of section S1 plus half thevoltage of section A of winding W2, resistance R splitting the voltageof section A as it did when brushes 4i and "i2 occupied similarpositions as earlier above described. Bearing in mind that theZero-voltage tap 2-3 is permanently connected by conductor 2! to theoutput terminal II, the potential applied to the companion outputterminal i5 will be seen to be the potential of section S1, to which hasbeen added the split voltage of section A of winding W2. Thus from tapE4 the circuit extends by conductor G4, contact M, brush El, slip ring12, brush it, conductor l, to tap 35 or" winding W2, that being theseries connection effected between the two windings. By conductors 56and 51, section A of winding W2 is connected to contacts G and J, acrosswhich, by brushes 4i and 42, resistance il is bridged, and, by thevariable tap 45, any fraction of the voltage of serially-connectedsection A of winding W2 is added to the voltage of section S1 andapplied to the companion output terminal I6.

From this point on, the successive steps above described are repeated,Vernier switch 35 adding successive voltage increments as abovedescribed, while brushes 5l and B8 of coarse switch 35 coact withcontacts M and O in successive steps as they did before coacting withcontacts L and M. When the full voltage of winding W2 has been added tothe voltage of section S31- which means that these two parts areconnected in series across the output terminals I6 and il through oneportion of the resistance i4- the process or steps are repeated, but nowby adding successive increments of voltage from the winding W2 to thevoltage of sections S1 and S2, which latter thus, for this succeedingcycle, function as a single section.

When Vernier switch 36 has again completed a single turn, bringing thevoltage across it to the output terminals I5 and Il equal to the sum ofthe voltages of sections S1 and S2 and winding 'W2- that voltage beingequal to the voltage of the three sections S1, S2, and S3-the switchesnow begin to add, in the next stage or cycle, successive increments ofvoltage from the winding W2 to the entire winding W1. To effect thattransition, contact P of coarse switch 35 is longer, so that brushes 67and -traveling at increased rate, due to the elliptical gearing-remainin contact with contact P, which, through conductors 66 and 22, isconnected to the end terminal '26 of the primary winding W1 as theseries connection with the primary winding W1 is made to the secondarywinding W2. From that point on, successive increments of rotary motionof the parts of Vernier switch 35 add to the voltage of the winding W1successive increments of voltage of the secondary winding W2, in themanner earlier above described, for impression upon the output terminalsIB and II, so that the maximum voltage-namely, the sum of the voltagesof windings W1 and W2--may be ultimately impressed upon the outputterminals and, hence, upon the load I9. From that point on the switchingarrangement moves into the initial starting positions of the partsinitially described above, whence the entire cycle may be repeated.

These successive increments of rotary motion may be manually effected bythe hand wheel 39, while the dial 81, appropriately graduated, serves,in coaction with the indicator or pointer 3B, to indicate the voltageapplied across the output terminals it and I I--the coarse switch 35 andthe pointer 86 making one complete revolution for the complete cycle ofvoltage change from zero voltage to the sum of the voltages of windingsW1 and W2. The elliptical gears 80 and BI have a ratio of drive of l tol, while the ratio of drive between gears 83 and 84 is l to the sum ofthe number of sections in the primary winding W1 plus l; where thewinding W1 has three sections, the ratio of drive is thus l to 4.

As above pointed out, the relationship of the parts and their coactionsmake it possible to achieve many practical advantages, and the switchparts, in particular, may be made small, permitting the use of materialslike silver throughout, and diminutiveness and compactness ofconstruction of the switch mechanism are readily achievable, making itpossible to provide the switch and switch mechanism, together with thetransformer itself, as a small compact, and light-weight unit, ideallysuited in such case for laboratory and test purposes. The system andapparatus have high electrical efficiency, excellent regulation, andhigh efficiency of commutation. In this latter connection I am enabledto achieve definite limitation or control of shortcircuit current duringcommutation, the relation of the resistance 44 being, by the switchingconstruction, always maintained, for any commutating transition, suchthat it functions to limit or control short-circuit current, and thus,also, the transformer windings are effectively protected againstoverload and need not be designed or wound to cope with such relativelyuncontrollable and widely variable factors as are inherent in the use ofcarbon brushes employed in heretofore known apparatus and which, as isknown,

frequently cause so-called hot spots in the transformer winding. Thesefactors all contribute toward achieving substantial reduction in sizeand weight over known types of voltagevarying apparatus of equal ratingor load capacity.

In Fig. 2 I have shown, in exploded or schematic perspective, how I amenabled to achieve still further compactness of construction andarrangement-in that, instead of arranging the Vernier switch and coarseswitch substantially side by side, as in Fig. l-and, hence, with theirshafts 33 and il in parallel alignmentmay arrange one switch mechanismin back of the other and align them coaxially so that, by making oneshaft hollow or tubular, the other shaft may il extend through it and,hence, be coaxial with it. Thus, in Fig. 2, I may arrange the coarseswitch in front of the vernier switch 36, and, by making the shaft ofcoarse switch 35 hollow or tubular-as indicated at lla-the shaft 38 ofthe Vernier switch 36 passes forwardly through it and thereby, also, asshown in Fig. 2, the hand wheel 39 and the dial and pointer 81-86 may bebrought to the front of the apparatus coaxially and closely adjacent toeach other. The geared driving connections between the two switchescomprise the gears, as in Fig. 1, together with an intermediate idlershaft 82-being simply and appropriately rearranged, as indicated in Fig.2, to function in the space between the rear of the plate 62 of thecoarse switch and the front face 3l of the Vernier switch. Any suitablebearings may be provided for the tubular shaft lla, while the latter canconveniently form a bearing for the vernier switch shaft 38. v

It will be understood that the transformer T of Fig. 1 is illustrativeof a possible relative arrangement o'f its parts and windings,.and thatvarious other relative arrangements of windings may be employed. Forexample, should it be desired that the transformer T also function as anisolating transformer, it may be constructed and arranged in the mannerindicated in Fig. 2, where I provide the transformer core R with aprimary winding 9| which is connected by con- 1 ductors 92 and 93 to thesource l5. In this arrangement the transformer retains the windings W1and W2, as shown in Fig. 2 and as they were described in connection withFig. 1, and they may have the same relative number of turns andsections, and, in relation to the primary winding 9|, the ratio of thenumber of turns or of voltage transformation, as between the winding 9|and the winding W2, may be of any desired value-illustratively 1 to l.In such case the vwindings W1 and W2 serve as secondary windings withrespect to winding 9i functioning as a primary transformer winding, andthe windings W1 and W2, and the circuits. connected thereto all as shownin Fig. Z-are thus isolated and insulated from the electrical circuit ofprimary winding 9i, the transformer in such case embodying any suitableinsulating construction or material, in known manner, as may be desiredor as is suitable for the particular. application. In such case, also,the apparatus may be provided with terminals 94 and 95 to function asinput terminals corresponding to the input terminals l l and l2 of Fig.1, and it has the same circuit arrangement, in so far as the windings W1and W2 and the two switches are concerned, as in Fig. 1, excepting thatthe tap or terminal 26 of the winding W1 is not connected to an inputterminal and, hence, terminal 26 is connected by conductors 22 and 66directly to the contact P.

In the form of both Figs. l and 2, the spaces between the contact platesand the switches 35 and 36 are preferably filled in so that the brusheslil-42 and 6l-63, as the case may be, have a substantially continuous oruninterrupted plane succession of surfaces to engage and transverseduring their rotary movements; such an ar rangement may be achieved inany suitable way -as, for example, by recessing the arcuate contactplates into the respective supporting plates 3l and 62, which are madeof insulating material, and such an illustrative arrangement is intendedto be shown or indicated in the drawings, but in Fig. 1 a dead contact Yis illustrated between contacts E and K, by which the wiping contact 12may be prevented from falling down between contacts E and K if thelatter are elevated above the plate 3l. Fatigue of the flat spring-likewiping contacts or brushes 5I-42 and 61-68 and loss of their springtension, by which they maintain good electrical contact, are thusprevented.

It will thus be seen that there has been provided in this invention asystem and switching arrangement in which the various objectshereinbefore noted, together with many thoroughly practical advantages,are successfully achieved. I am enabled to achieve exceeding compactnessof construction and high efciency, with low iron losses and low contactresistance losses, the latter being greatly lessened or minimized wheresilver or like highly conductive metals are employed for the brushes andcontact elements, and, moreover, I am enabled to achieve fine or smallincrements of voltage change. Physically the transformer and switchingmechanism, for a given range or capacity, can be embodied in small andcompact form and thus, in contrast to known types of systems andmechanisms, I am enabled to achieve high efficiency of space.

As many possible embodiments may be made of the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth, or shown in theaccompanying drawing, is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. Means for providing variable voltage in contrcllable incrementscomprising a group of inductive windings each of relatively largevoltage, a group of inductive windings each of relatively small voltage,a resistance having an intermediate tap, output terminals respectivelyconnected to a terminal of one of said groups of windings and to saidresistance tap, two make and break rotary switching means, each of whichhas rotatable brush means and arcuate contact means coacting therewith,one of said rotary switching f means having connections between itsbrush means and contact means and the windings of said second group andsaid resistance to effect, upon rotary movement of said brush means,successive addition in serial relation of the windings of said secondgroup and to impress the resultant Voltage upon said output terminals byway of said resistance tap and alternately through only a portion ofsaid resistance and through said resistance in parallel relation to theadded windings of said second group, the other of said rotary switchmeans having connections between its brush means and arcuate contactmeans and the windings of said first group to effect, upon rotarymovement of said brush means, addition in serial relation of successivewindings of said first group with respect to the windings of said secondgroup, and driving connections between the two rotary brush means ofsaid two rotary switching means to effect such ratio of drive andvarying ratio of angular velocities between said two brush means tocause addition of a winding of said first group in serial relation tothe windings of said second group only after the voltage of all of thewindings of the second group has been impressed upon said outputterminal in successive increments and to thereafter add the voltage ofthe windings of said second group in successive increments to the addedwindings of saidv first group and means for driving the said first brushmeans at an accelerated rate in passing between adjacent contacts.

2. A variable voltage means as claimed in claim l, in which the rotaryswitch means that affects the connections of the windings of said secondgroup comprises also two stationary spaced brushes connected to the endsof said resistance, the rotary brush means comprising two brush elementscoacting with the arcuate contacts of said rotary switching means andhaving arcuate Contact elements respectively coacting with saidrst-mentioned two brushes.

3. A voltage regulating system comprising, in combination, a firstinductive winding divided into a plurality of sections, means forenergizing said winding from an A. C. source, the output voltages ofsaid sections being substantially equal, a second inductive winding andmeans for energizing said second winding from said source to producetherein an output voltage substantially equal to the voltage of one ofsaid sections, contact taps dividing said second winding into aplurality of substantially equal subdivisions, an impedance elementhaving a tap at an intermediate point thereon, a pair of power outputterminals, the rst of said terminals being connected to said impedancetap, and a switching means having a plurality of cooperating movable andstationary contacts, said switching means being operable in a firstseries of positions to :a

connect said second output terminal to one end of said second winding,and in successive series of positions to connect said second outputterminal to said end of said second winding through Y successively addedsections of said rst winding,

combination, a rst inductive winding divided in- 'r to a plurality ofsections, means for energizing said winding from an A. C. source, theoutput voltages of said sections being substantially equal, a secondinductive winding and means for energizing said second winding from saidsource 14 to produce therein an output voltage substantially equal tothe voltage of one of said sections, taps dividing said second windinginto a plurality of substantially equal subdivisions, a resistanceelement having a tap at an intermediate point thereon, a pair of poweroutput terminals, the irst of said terminals being connected to saidresistance tap, and switching means having a coarse switch section and avernier switch section,

e each of said sections having a plurality of cooperating movable andstationary contacts, said coarse switch section being operable in a rstswitch position to connect said second output terminal directly to oneend of said second winding and in successive switch positions to connectsaid second output terminal to said end of said second winding throughsuccessively added sections of said rst winding, said Vernier switchsection being operable in successive positions to connect the ends ofsaid resistance element across successive individual subdivisions ofsaid second winding, said Vernier switch section eiecting transfer ofsaid resistance element connections from one subdivision to the nextsucceeding subdivision by disconnecting one end of said rei sistanceelement from a tap of said second winding and subsequently connectingsaid end to the second succeeding tap while maintaining the connectionof the other end of said resistance to the first succeeding tap,rotatable drive shafts supporting the movable contacts of said switchsections, a manual control handle on the Vernier drive shaft, and acyclically variable ratio drive coupling between said Vernier driveshaft and the coarse switch drive shaft whereby the contacts of the saidcoarse switch are driven at an accelerated speed in passing between someof the xed contacts.

JOHN A. GULOW.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 734,438 Skinner July 21, 19031,961,801 St. Palley July 5, 1934 2,085,255 Emlen et al June 29, 19372,112,046 Puller et al Mar. 22, 1938 2,114,143 Hunter Apr. 12, 19382,138,652 Biermans Nov. 29, 1938 2,146,914 Rauhut Feb. 14, 19392,210,688 Schmutz Aug. 6, '1940 2,431,023 Browne Nov. 18, 1947

